1. Field of the Invention
The present invention relates to an angular speed detecting apparatus for a crankshaft of an internal combustion engine, which detects a rotational angular speed of the crankshaft of the engine, and particularly, to an angular speed detecting apparatus having a pulse generator for generating a crank pulse at every predetermined rotational angle and correcting a time interval of when the crank pulse is generated.
2. Description of the Related Art
Japanese Patent Publication No. 3571043 (JP-'043) discloses a method for correcting a time interval of when the crank pulse is generated in a pulse generator which generates the crank pulse at every predetermined rotational angle of the crankshaft of the internal combustion engine. According to the disclosed method, a ratio of an amount of change in the time interval of when the crank pulse is generated during engine braking is calculated, and a correction value of the time interval of pulse generation is calculated by averaging data of the calculated ratio.
Even in a condition where fuel is not supplied to the engine during engine braking, a rotational speed changing component attributed to the inertial forces of the movable parts of the engine is contained in the detected time interval of pulse generation. Therefore, if the correction value calculated by the method shown in JP-'043 is applied, the time interval of pulse generation is obtained, but without accounting for the influence of the rotational speed changing components.
On the other hand, when a misfire determination is performed based on the time interval of pulse generation, it is necessary to remove the influence of the rotational speed changing component attributed to the above-described inertial forces from the detected time interval of pulse generation in order to accurately perform the misfire determination. If the above-described conventional correction method is applied, the rotational speed changing component is removed with a component due to a mechanical deviation of the pulse generator. Accordingly, accurate misfire determination cannot be performed using the conventional correction method.